Plagues of rats devastate rice fields in Mizoram every 48 years. Vast numbers of black rats take advantage of the bamboo flowers that are only available twice a century, then turn their attention to farmers' crops when the flowers becomes scarce.
Black Rats and Brown Rats
The Black Rat (Rattus rattus) is a natural inhabitant of Asian bamboo forests, where it is typically present in small numbers. Black Rats spread through the Near East to Europe, and then widely across the world, as humans moved them accidentally from place to place in historical times.
Black Rat parasites (fleas) were responsible for the outbreaks of bubonic plague that occurred across Europe during the fourteenth century (the 'Black Death' killed one third of Europe's population at that time).
The black rat is best adapted for life in tropical bamboo forests, but it used to survive well around humans in northern climes until it was replaced there by the Brown Rat (Rattus norvegicus) in recent times. Most pet rats, and all laboratory rats are descended from Brown Rats.
Black Rats and Bamboo Flowering in Mizoram
Small populations of Black Rats live the bamboo forests of India. The species of bamboo that predominates in the state of Mizoram (North East India) flowers once every 48 years and when this happens the rats suddenly have a superabundance of food, and the population explodes.
In the years when there was a vast supply of bamboo flowers to eat (1863, 1910/11, 1958/59, 2006/7) these rat plagues went on to cause famines and outbreaks of disease – there was also violence back in 1959 (BBC News).
Why this species of bamboo (Melocanna baccifera) should only flower once every 48 years is a bit of a mystery. One theory is that it saves up all its energy to produce vast numbers of fruits at the same time so that the rats can't eat them all and sufficient survive to germinate and grow into the next forest (the parent plants die after flowering). Another theory suggests that lightning causes fires that burn off the old, dead, forest – leaving clear ground for germination and growth of the next generation. (The truth might well be a bit of both!).
Rats, Bamboo, and Mautam in Mizoram
The regular occurrence of rat plagues and famine in Mizoram is known as the 'mautam' (YouTube video – ' Mautam in Mizoram '). Local oral tradition relates that twice a century, when the bamboo flowers, there will be a plague of rats followed by a famine.
In the past there were few roads in the region and it was not possible to get food in to places where the famine had struck, but by 2006/7 there was better communication and more efficient food relief was possible. In addition to this the precise relationship between the rats and the bamboo was better understood, and several things made the problem less severe:
- a bounty of one rupee was paid for each rat tail, and over two hundred thousand rats were killed in 2006
- alternative crop plants were grown in order to reduce the dependence on rice
- people were encouraged to eat rats as an alternative food source.
Hopefully people will be even better prepared when the mautam strikes Mizoram again in 2054.
Reference:
'famine caused by rats' - BBC News, 2007.
Join the Conversation